Re: [PATCH] pivot_root broken in 2.6.15-rc1-mm2

[Rob Landley <rob@landley.net>]

On Wednesday 23 November 2005 23:09, Neil Brown wrote:
> On Wednesday November 23, rob@landley.net wrote:
> > On Tuesday 22 November 2005 20:07, Neil Brown wrote:
> > > Pivot_root seems to be broken in 2.6.15-rc1-mm2.
> > >
> > > I havea initramfs filesystem, mount a ext3 filesystem (which has /mnt)
> > > at '/root' and
> > >
> > >   cd /root
> > >   pivot . mnt
> > >
> > > and it says -EINVAL.
> >
> > You can't pivot_root initramfs because initramfs is rootfs.
> >
> > I wrote Documentation/filesystems/ramfs-rootfs-initramfs.txt just for
> > this occasion. :)
>
> Unfortunately, 'man pivot_root' nor 'use the source, Luke' contain
> pointers to this particular useful document.  They both list assorted
> restrictions on pivot_root, but not this one.
>
> How about the following?
>
> Thanks,
> NeilBrown
>
> Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Rob Landley <rob@landley.net>

> ### Diffstat output
>  ./fs/namespace.c |    4 ++++
>  1 file changed, 4 insertions(+)
>
> diff ./fs/namespace.c~current~ ./fs/namespace.c
> --- ./fs/namespace.c~current~ 2005-11-23 14:24:59.000000000 +1100
> +++ ./fs/namespace.c 2005-11-24 16:07:01.000000000 +1100
> @@ -1526,6 +1526,10 @@ static void chroot_fs_refs(struct nameid
>   * pointed to by put_old must yield the same directory as new_root. No
> other * file system may be mounted on put_old. After all, new_root is a
> mountpoint. *
> + * Also, the current root cannot be on the 'rootfs' (initial ramfs)
> filesystem. + * See Documentation/filesystems/ramfs-rootfs-initramfs.txt
> for alternatives + * in this situation.
> + *
>   * Notes:
>   *  - we don't move root/cwd if they are not at the root (reason: if
> something *    cared enough to change them, it's probably wrong to force
> them elsewhere)